Staged accelerator pump for two-stage carburetor

ABSTRACT

Lever and linkage mechanism are disclosed for staged or sequential operation of the accelerating pump of a two-stage carburetor. The linkage mechanism is so arranged that the accelerating pump is caused to travel during an initial opening of the primary valve of the carburetor, after which the pump ceases to move until the secondary throttles begin to open, at which time additional pumping action is accomplished by the accelerator pump.

United States Patent Inventor: John L. Niebrzydoski, Florissant,

Assignee: ACF Industries Incorporated, New

York, NY. I

Filed: Aug. 23, 1971 Appl. No.: 174,016

US. Cl. 261/23 A, 261/34 A, 261/34 B Int. Cl. F02m 7/08 Field of Search 261/34 A, 23 A, 34 13 References Cited UNITED STATES PATENTS 6/1960 Braun 261/23 A Niebrzydoski [4 Oct. 9, 1973 [54] STAGED ACCELERATOR PUMP FOR 3,045,505 7/1962 Boehlow 261/34 A TWOSTAGE CARBURETOR 3,208,738 9/1965 Johnson 261/34 A 4/1971 Szwargulski et a1. 261/23 A Primary Examiner-Tiin R. Miles Attorney-Edward H. Casey [5 7] ABSTRACT Lever and linkage mechanism are disclosed for staged or sequential operation of the accelerating pump of a two-stage carburetor. The linkage mechanism is so arranged that the accelerating pump is caused to travel during an initial opening of the primary valve of the carburetor, after which the pump ceases to move until the secondary throttles begin to open, at which time additional pumping action is accomplished by the acc elerator pump.

4 Claims, 6 DrawingFigures PATENTEU 3,764.1 19

SHEET 1 (IF 2 I9 J FIGURE I.

y iv 90 7 I INVENTOR JOHN L. NIEBRZYDOSKI ATTORNEY PAIENTED 91975 3.764.119

sum REF 2 FIGURE 6.

FIGURE 5.

INVENTOR JOHN L. NIEBRZYDOSKI ATTORNEY STAGEI) ACCELERATOR PUMP FOR TWO-STAGE CARBURETOR BACKGROUND OF THE INVENTION Two-stage carburetors, well known in the prior art, typically are exemplified in the United States by the well known four-barrel carburetor. Such a carburetor has a pair of primary throttles and a pair of secondary throttles which, by way of suitable linkages, are caused to open in a sequential manner. When both throttles are fully opened, the engine is enabled to deliver maximum performance. In a typical carburetor of the fourbarrel variety, an accelerator pump is provided which delivers a small quantity of additional fuel during opening movement of the primary throttle. This additional fuel is usually necessary if the rapid and immediate response that the public is accustomed to is to be realized. In most such carburetors, after a predetermined amount of opening of the primary throttle, the accelerator pump no longer delivers additional fuel either because it has reached the end of its travel, or because a stop mechanism has been brought into action to prevent any such additional travel. The result of this situation is that the accelerator pump is not available to make an initial discharge of fuel upon opening of the secondary'throttles. To overcome this, various schemes have been employed to initiate flow of fuel from the secondary fuel nozzles. In some instances, a spring biased air valve has been installed in the secondary side of the carburetor above the fuel nozzles. In such a case it is intended that when the secondary throttles begin to open there will be an initial suction placed on the fuel nozzles before the air valve begins to open. This preliminary suction on the fuel nozzles is intended to provide the necessary fuel to start the operation of the secondary side of the carburetorin such a manner that no hesitation or stumble will result. In other instances, this has been found to be somewhat inadequate and various forms of dashpots have been applied to the air valve to hold it closed for a slight additional amount of time. The foregoing expedients have not always been satisfactory in that there has not always been a smooth transition from operation of the primary side of the carburetor to the secondary side of the carburetor.

One carburetor'of the type just described is shown in greater detail in the US. Pat. to Szwar'gulski et al No. 3,575,385 dated Apr. 20, I971, and entitled THROT- TLE LINKAGE MECHANISM FOR A MULTI- STAGE CARBURETOR."

It is an object of the invention to provide a carburetor having primary and secondary linkages so arranged that as the primary throttles begin an opening movement the accelerating pump will be caused to move in a discharging direction after which the same will become stationery and then when the secondary throttles begin to open the accelerating pumpwill resume its downward movement to discharge additional fuel upon initial opening of the secondary valves.

BRIEF DESCRIPTION'OF THE INVENTION In the carburetor of this invention there is provided on the primary throttle shaft a lever which is fixed to the shaft and a second lever which is loose on the shaft. After a predetermined amount of opening of the pri mary throttle, the fixed lever picks up the loose lever. The loose lever is connected by way of a link to a loose lever on the secondary throttle shaft. The secondary throttle loose lever is provided with a tang on one side of the lever. Also mounted on the secondary throttle shaft, and in fixed relation thereto, is a second lever arm which is the operating lever for the secondary throttle. Pivoted upon the operating lever is a latch which can rotate into and out of engagement with the tag on the loose lever. Through suitable linkages the choke valve of the carburetor is connected to a rocker arm which moves in accordance with the position of the choke. When the choke is fully opened, the rocker arm by way of a tab moves the latch into engagement with the tang on the secondary throttle loose lever. Once the latch is engaged with the tang, movement of the loose lever then causes the fixed lever to move and the secondary throttles to open.

There is also provided on the primary throttle shaft a loose lever which actuates the accelerating pump of the carburetor. This pump operating lever is so arranged that it provides for over-travel whenever the accelerating pump bottoms out as the primary and secondary throttles are opened to the fully opened position. The pump operating lever is provided with a tang that is so arranged that as the primary throttles are opened from the closed position, the pump operating lever tang will contact a second tang on the loose lever on the primary throttle shaft which actuates the secondary throttles. When the two tangs are in contact the pump operating lever arm can no longer move until the first-mentioned loose lever is moved out of the way as occurs when the primary throttle is opened to the point at which it begins to actuate the secondary throttle.

Upon actuation of the secondary throttle, the pump operating lever is allowed to move an additional distance thereby delivering accelerating fuel to the carburetor at this critical point in the operation of the carburetor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side view of a two-stage carburetor having both primary and secondary throttles in which the throttles are at the normal curb-idle position.

FIG. 2 is a fragmentary 'side view of the primary throttle portion of the carburetor showing the primary throttles partly open.

FIG. 3 is a view similar to FIG. 2 having a wider opening of the primary throttle but showing that the accelerating pump is not moved from the FIG. 2 position.

FIG. 4 shows the primary throttleat still a more open position after the secondary throttles have begun to open and showing the accelerator pump as having bottomed out.

FIG. 5 is a partial section of a carburetor showing the accelerating pump well and piston.

FIG. 6 is a partial plan view showing a portion of the primary throttle shaft together with the levers and linkages'involved in the present invention.

DETAILED DESCRIPTION OF THE INVENTION may be separate from the body 12 as shown or may be integrally formed therewith. Fuel is supplied to an inlet fitting of the carburetor and is regulated by a fuel control valve of conventional nature. The primary side of the carburetor air horn is provided with a choke valve 18 mounted on a shaft 19. The choke valve control mechanism is not shown but can be manual or automatic as is well known in the art. A lever arm 20 on the choke shaft is connected by way of a link 21 to a countershaft 22. Thus countershaft 22 rotates as a function of rotation of the choke shaft 19. A lever 23 on countershaft 22 is connected by link 24 with fast idle arm 26. Fast idle arm 26 is rotatably mounted ona pivot pin 28 fastened to the throttle flange 16.v Arm 26 is provided with a fast idle adjustment screw 29 which coacts with a fast idle cam to speed up the engine during cold starting and warmup. As shown screw 29 is at the opposite end of fast idle arm 26 from the end which is connected to the choke countershaft. Arm 26 is further provided with a secondary throttle engagement tab 30 located at the end of arm 26 which also receives connecting link 24.

The carburetor is provided with a primary throttle shaft 40 and a secondary throttle shaft 41 which are respectively provided with a primary throttle 36 and a secondary throttle 38. Mounted on primary throttle shaft 40 is a fast idle cam 43 and a throttle lever 44. Throttle lever 44 is driven by way of a rod through the customary foot pedal on the interior of the vehicle. Fast idle cam 43 and throttle lever 44 are both fixed on the shaft 40. Loosely mounted on shaft 40 is a primary throttle shaft arm 46. Arm 46 has pickup ear 47 and a return ear 48. Throttle lever 44 is provided with a rearwardly turned ear engagement tab 45 which coacts with ears 47 and 48 as hereinafter described. Fast idle cam or lever arm 43 is provided with a cam surface 50 for increasing the speed of the engine when the engine is cold and is further provided with an idle speed adjustment surface 51 which by way of screw 52 adjusts the speed of the engine when the engine is warm. Screw 52 is threadably engaged with a boss 53 which is a part of air horn 14.

Primary throttle shaft arm 46 is connected by way of a link 60 to an operating lever 62 loosely mounted on secondary shaft 41. Loose lever 62 has an operating tang 63. Mounted on shaft 41 and in fixed relation thereto is a secondary throttle actuating lever 66 having a tang 67. A latching lever 68 is mounted on lever 62 by way of a pivot pin 69. Latch 68 is so arranged that its own weight normally causes the latch to fall into a downward position in which a tab 70 rests on the tang 30. This prevents the latch from dropping completely out of position. Lever 68 is provided with a latching surface or dog 72 which cooperates with the tang 63in a manner to be hereafter described. A coil spring urges loose lever into a normal throttle closed position and a coil spring urges throttle shaft 41 into a normally throttle closed position.

The operation of the carburetor as thus far described will now be given. With the choke closed or partly closed rod 24 moves the fast idle arm 26 to a low position. This low position causes the screw 29 on arm 26 to rise into engagement with the fast idle surface 50 thus propping the throttle open a small amount.

Upon additional opening movement of the primary throttle tab 45 on throttle lever 44 moves into engagement with pickup gear 47 thus causing lever 46 to move. Movement of lever 46 causes loose lever 62 to move by way of link 60. Because rod 24 is holding idle arm 26 in a low position, latch 72 is in a nonengagcable position and movement of lever 62 results in a condition where the tang 63 does not engage latching surface 72 (seeFlG. 6) and the primary throttle moves to a fully open position without movement of the secondary throttle.

A different result is obtained when the choke is fully opened indicating a warmed-up engine. When the engine is warm, rod 24 pulls idle arm 26 upwardly and this in turn causes screw 29 at the other end of arm 26 to move into a low position away from the fast idle surface 50 and at the same time pulls tab 30 upwardly to raise latch 68 into a position where it can and will engage the tab 63 of loose lever 62. Thus opening the primary throttle will result in tab 45 contacting pickup ear 47 thus causing loose lever 46 to drive loose lever 62 through link 60. Movement of lever 62 will cause tab 63 to engage latching surface 72 of latch 68 to drive lever 66 by way of pivot pin 69 and since lever 66 is fast on secondary throttle shaft 41 the secondary throttle 38 will open. When the primary throttle is returned to a closed position, a biasing spring will normally urge the secondary throttle into a closed position. However, to insure positive movement of the secondary throttle, tab 45 moves into engagement with return ear 48 and this in turn-drives loose lever 46 and hence lever 62 into a throttle closed position. At that time the tang 63 contacts latch 68 and this also forces the secondary throttles into a closed position.

Another important feature of the invention resides in the accelerator pump-actuating control. The carburetor is provided with an accelerating pump (FlG. 5) which is of the type that is biased in the pumping direction by a spring 89 inside the pumping chamber. A stem 90 holds the pump piston in an uppermost position when thethrottle is closed and when the stem 90 is released the internal spring forces the piston downwardly to cause the pump to discharge a metered amount of fuel. A link 92 connects the stem 90 to a pivoted lever 94. When the stem 90 moves downwardly link 92 strikes a boss 91 to limit the travel of the pump.

Lever 94 is pivoted at 95. A link 96 connects an end of lever 94 with a loose lever 98 which is rotatably mounted on primary throttle shaft 40. Lever 98 has an extension witha tab 100 and loose lever 46 has a tab 102. Tabs 100 and 102 are so formed that the tab 100 will strike tab 102 when lever 98 moves in an upward direction.

Lever 46 which may also be termed the secondary throttle driving lever, is biased in a direction to close the secondary throttles by way of a spring 106 which encircles primary throttle shaft 40 and has an end 107 which bears against loose lever 46 and another end 108 which bears against lever 43 which is fixed to shaft 40. Thus, lever 46 is normally urged in a direction to urge the secondary throttles in a closing direction.

In operation if it is assumed that the primary throttle 36 is closed and that the accelerator peddle is moved in a direction such as to open the primary throttles, then the movement of shaft 40 causes lever arm 43 to move in a throttle-opening direction and arm 46 has upon it a reversely directed tab 110 which moves out of the way of a tab 112 on arm 98. This allows link 96 to move upwardly allowing lever 94 to pivot upon the pin 95 and this in turn allows stem 90 to move downwardly under the influence of the spring which urges the pump piston 122 to move downwardly thus displacing fuel from the pump chamber 124 which in turn causes a discharge of fuel into the mixing chamber of the carburetor thus providing the desired acceleration fuel. This initial movement of the throttle can be seen by comparison of FIG. 1 with FIG. 2.

Upon-additional movement of the primary throttle, the tab 100 strikes tab 102 (see FIG. 2) and at this point the accelerator pump ceases movement because the biasing spring 106 is of sufficient resistance to prevent further movement of the loose lever 98. As the primary throttle is opened further tab 102 is moved up wardly and tab 100 follows with it so that additional movement of lever arm 98 occurs. This occurence is coexistent with the initial opening of the secondary throttles. Thus, as the secondary throttles are partially opened, the mechanism moves to the position shown in FIG. 3 at which time the secondary throttles are not completely opened. FIG. 4 shows the situation where additional opening movement of the primary and secondary throttles-has taken place and where the tab 102 of secondary throttle driving arm 46 has moved into its maximum, position. At that time, tab 102 has moved away from tab 100 of arm 98 showing that the pump 122 has reached its maximum extension prior to the time the secondary throttles are fully opened.

From the foregoing it will be seen that a sequential type operation is imparted to the accelerating pump of the staged carburetor. This sequential action is so arranged that upon an initial opening movement of the primary throttle valves the accelerating pump is allowed to move downwardly in a discharging direction until a tab on the accelerating pump actuating lever contacts a second tab on a portion of the mechanism which controls operation of the secondary throttle. Thereupon, the accelerating pump ceases its discharging movement until the carburetor is'called upon to deliver additional power by way of opening of the secondary throttle. As the secondary throttle actuating mechanism is moved inan opening direction'by the primary throttle, then the stop tab on the secondary throttle actuating lever moves out of the way to allow the accelerating lever arm to resume its movement thus allowing the accelerating pump to resume discharge.

I claim:

bin a multi-stage carburetor having a primary throttle moveable by a primary throttle shaft, a secondary throttle moveable by a secondary throttle shaft, lever and linkage mechanism for the sequential operation of said throttles as a function of the opening movement of said primary throttle shaft and an accelerating fuel pump moveable to discharge fuel as a function of movement controlled by movement of said primary throttle shaft, the improvement comprising:

A. An accelerating fuel pump in a well in a fuel bowl of said carburetor, said pump having a stem and a biasing spring for urging said pump in a pumping direction,

B. A pivoted lever attached at a first end to said stem and'having an operating link at its second end,

C. A pump operating lever pivotable mounted on said primary throttle shaft, said operating lever having a tab struck from an end thereof, said operating lever being connected to said link, said operating lever also having a releasing surface cooperable with a tab connected to a primary throttle shaft lever arm whereby said release surface is allowed to move when said le-ver arm is moved,

D. A secondary throttle drive lever fitted on said primary shaft and connected by a link to a secondary throttle lever arm, said secondary throttle drive lever having a stop tab attached thereto,

E. A driving tab attached to said primary throttle shaft lever am, said driving tab adapted to contact said secondary throttle drive lever after a predetermined movement of said primary throttle shaft, thereby to initiate opening of said secondary throttle,

F. Said tab on said operating lever and said stop tab being'arranged so that an initial movement of said primary throttle shaft will allow said operating lever to complete an initial movement and come to a stop and after additional movement of said primary lever, said stop tab being moved out of the way of said tab on said operating lever.

2. The carburetor of claim 1 further comprising a spring for biasing said secondary throttle drive lever to a normally-closed secondary throttle position.

3. The carburetor of claim 2 further including a fast idle cam fixed to said primary throttle shaft, said fast idle cam including a pump return tab adapted to contact a surface of said operating lever to move said pump in a direction to fill said pump when said primary throttle is closed.

4. The carburetor of claim 2 further including a fast idle arm pivoted about a point on said carburetor and having a latching tang at one end thereof, said tang being cooperable with a latching lever on a secondary throttle shaft lever arm to prevent movement of said secondary throttle during low temperature operation and to permit movement during normal temperature operation.

. i 1K t 

1. In a multi-stage carburetor having a primary throttle moveable by a primary throttle shaft, a secondary throttle moveable by a secondary throttle shaft, lever and linkage mechanism for the sequential operation of said throttles as a function of the opening movement of said primary throttle shaft and an accelerating fuel pump moveable to discharge fuel as a function of movement controlled by movement of said primary throttle shaft, the improvement comprising: A. An accelerating fuel pump in a well in a fuel bowl of said carburetor, said pump having a stem and a biasing spring for urging said pump in a pumping direction, B. A pivoted lever attached at a first end to said stem and having an operating link at its second end, C. A pump operating lever pivotable mounted on said primary throttle shaft, said operating lever having a tab struck from an end thereof, said operating lever being connected to said link, said operating lever also having a releasing surface cooperable with a tab connected to a primary throttle shaft lever arm whereby said release surface is allowed to move when said lever arm is moved, D. A secondary throttle drive lever fitted on said primary shaft and connected by a link to a secondary throttle lever arm, said secondary throttle drive lever having a stop tab attached thereto, E. A driving tab attached to said primary throttle shaft lever arm, said driving tab adapted to contact said secondary throttle drive lever after a predetermined movement of said primary throttle shaft, thereby to initiate opening of said secondary throttle, F. Said tab on said operating lever and said stop tab being arranged so that an initial movement of said primary throttle shaft will allow said operating lever to complete an initial movement and come to a stop and after additional movement of said primary lever, said stop tab being moved out of the way of said tab on said operating lever.
 2. The carburetor of claim 1 further comprising a spring for biasing said secondary throttle drive lever to a normally closed secondary throttle position.
 3. The carburetor of claim 2 further including a fast idle cam fixed to said primary throttle shaft, said fast idle cam including a pump return tab adapted to contact a surface of said operating lever to move said pump in a direction to fill said pump when said primary throttle is closed.
 4. The carburetor of claim 2 further including a fast idle arm pivoted about a point on said carburetor and having a latching tang at one end thereof, said tang being cooperable with a latching lever on a secondary throttle shaft lever arm to prevent movement of said secondary throttle during low temperature operation and to permit movement during normal temperature operation. 